Unit Converter
Length, weight & temperature.
Unit Converter at a glance
Unit Converter is a free online converter you can use right now to length, weight & temperature โ no account, no install and no usage limit. It runs entirely inside your browser, so whatever you enter stays on your own device.
- Price
- Free โ no trial, no paid tier, no watermark
- Sign-up
- Not required
- Where it runs
- In your browser โ nothing is uploaded to a server
- Works on
- Chrome, Safari, Firefox and Edge โ desktop, tablet and phone
- Category
- Converters
About Unit Converter
Convert between metric and imperial units across length, weight and temperature in one place.
Temperature behaves differently from every other conversion here, and it is worth understanding why. Length and weight scales share a zero point โ zero metres is zero feet, zero kilograms is zero pounds โ so converting is a single multiplication. Celsius and Fahrenheit do not: zero Celsius is 32 Fahrenheit. That offset means temperature conversion needs both a multiplier and an addition, which is also why a temperature difference converts differently from a temperature. A rise of 10ยฐC is a rise of 18ยฐF, not 50ยฐF.
Many imperial-to-metric factors are exact by definition rather than measured approximations. The inch is defined as precisely 2.54 centimetres and the pound as exactly 0.45359237 kilograms, both fixed by international agreement in 1959. Rounding those in a calculation introduces error that was not there in the definition.
The unit worth being most careful with is the gallon, because the US and imperial versions differ substantially โ a US gallon is about 3.79 litres and an imperial gallon about 4.55, a difference of roughly 20%. Recipes, fuel figures and container volumes all suffer from this, and the unit is rarely qualified in writing.
How to use Unit Converter
- Choose what you are converting โ length, weight or temperature.
- Enter your value and pick the units to convert from and to.
- Read the result along with the conversion factor.
Frequently asked questions
Why does temperature need a formula rather than a factor?
Because Celsius and Fahrenheit do not share a zero point. Scales starting from the same zero convert by multiplication alone. Zero Celsius is 32 Fahrenheit, so the conversion needs a multiplier and an offset.
Is 1 inch exactly 2.54 cm?
Yes, exactly โ it was defined that way by international agreement in 1959. The pound is likewise exactly 0.45359237 kilograms. These are definitions rather than measurements.
Is a US gallon the same as an imperial gallon?
No, and the difference is large. A US gallon is about 3.79 litres, an imperial gallon about 4.55 โ roughly 20% more. Since text rarely specifies which is meant, this causes real errors in recipes and fuel figures.
How do I convert a temperature difference?
Multiply by 9/5 without adding the offset. A rise of 10ยฐC is a rise of 18ยฐF. The +32 applies only when converting an absolute temperature, not a change in one.